The long term objectives of this proposal are to study the development of intrinsic inhibitory influences on cortical function. Morphologically, synaptogenesis in the cortex proceeds through stages. This series of experiments is designed to study in detail the maturation of function associated with elaboration of intracortical circuitry during early development. The relatively simplified general cortex of the turtle Pseudemys scripta has been selected as a preparation ideally suited for study. The cellular differentiation of the inhibitory interneuron of the turtle and its normal target cell, the cortical pyramidal neuron, will be explored. The timetable of development of inhibitory synapses onto the pyramidal cell will be established along with a detailed characterization of the post synaptic inhibitory receptor, its ontogenesis and topographical distribution through early developmental stages. Methods will include conventional intracellular recording techniques, membrane patch clamp, and the application of monoclonal antibody labels. Since inhibitory control over cortical excitability can play a key role in epileptogenesis, these studies will form a necessary background for the study of epilepsy in the developing cortex.